One Rep Max (1RM) Calculator

Use this one rep max (1rm) calculator for an approximate adult fitness calculation. Choose US units for pounds, inches or yards, or switch to metric. Results are estimates, not medical or training prescriptions.

Your Numbers

Weight Liftedkg

Repetitions Completedreps

Results

Estimated 1RM (average)—

Epley Estimate—

Brzycki Estimate—

85% Working Weight—

Input check—

Results update live as you type. Estimates only — not financial, tax, or investment advice.

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The Formula

Epley: 1RM = weight × (1 + reps ÷ 30); Brzycki: 1RM = weight × 36 ÷ (37 − reps)

Understanding the One Rep Max (1RM) Calculator

Worked example: Lifting 100 kg (220.5 lb) for five repetitions gives Epley 116.67 kg and Brzycki 112.5 kg; their average is 114.58 kg (252.6 lb).

Prediction accuracy varies with exercise, fatigue and repetition count. The 85% result is a mathematical comparison, not an instruction to attempt an unfamiliar load.

Frequently Asked Questions

How is the result calculated?

Epley: 1RM = weight × (1 + reps ÷ 30); Brzycki: 1RM = weight × 36 ÷ (37 − reps)

What should I know about this estimate?

Prediction accuracy varies with exercise, fatigue and repetition count. The 85% result is a mathematical comparison, not an instruction to attempt an unfamiliar load.